1. Technical Field
This invention relates to compositions for cleaning glassware. More particularly, it relates to glassware cleaning compositions for use in automatic dishwashing machines of the Industrial and Institutional (I&I) type wherein the compositions afford glassware protection.
2. Background Art
Compositions for use in dishwashing wherein the compositions afford glassware protection are well known. These are described in U.S. Pat. Nos. 2,575,576; 3,255,117; 3,350,318; 4,416,794 and 4,443,270 which teach the use of soluble zinc salts for this purpose. In U.S. Pat. No. 2,575,576 a water soluble zinc salt is employed to prevent the corrosion of vitreous and ceramic surfaces. In U.S. Pat. Nos. 3,255,117 and 3,350,318 soluble zinc salts are described for use in automatic dishwashing detergent compositions. In U.S. Pat. No. 3,677,820 it is taught that solid plates of zinc metal alloys are placed in contact with the use concentration of the detergent composition where the metal zinc slowly dissolves, and thereby needs occasional replacement to provide corrosion protection to glassware. A soluble zinc salt is disclosed in U.S. Pat. No. 4,443,270 in conjunction with a low foaming nonionic surfactant and in U.S. Pat. No. 4,416,794 zinc salts of chloride, sulfate or acetate are taught.
In U.S. Pat. Nos. 4,908,148 and 4,933,101 insoluble inorganic zinc compounds are employed in conjunction with a surfactant. However, relatively large amounts of the insoluble inorganic zinc compounds are required. Further, the inorganic compounds are suspended in the form of highly viscous liquids or slurries which present problems as further explained herein.
Notwithstanding the teachings of the prior art, there is a need for an improved liquid automatic dishwashing composition which can provide efficient cleaning in fast cycle I&I dishwashing machines yet provide glassware protection.
Accordingly, the objects of the invention are:
a. Providing an improved dishwashing composition.
b. Providing an improved dishwashing composition for use with fast cycle I&I dishwashing machines which employ highly corrosive alkaline materials.
c. Providing an improved dishwashing composition of the foregoing kind which utilize minimal amounts of zinc salts.
d. Providing an improved method of utilizing the foregoing kind wherein the zinc salt is low in toxicity.
e. Providing an improved method of utilizing the foregoing composition.